Solid-state electrolytic capacitor and method of making same

ABSTRACT

The method of making a capacitor by forming a piece of sheet metal to provide a common support and alternate anode and cathode members extending from the support, electrically connecting capacitor elements between each of said anode and cathode members, coating the individual elements and at least part of the anode and cathode members with a plastic resin and then severing the members from the common support and the resulting capacitor which has the terminals extending therefrom in substantially parallel relationship.

United States Patent Matsuo et al. 1 Feb. 29, 1972 [54] SOLID-STATEELECTROLYTIC 3,412,444 11/1968 Klein ..317/230 X CAPACITOR AND METHOD OF3,403,303 9/1968 Klein ....317/230 MAKING SAME 3,530,342 9/1970 Klein..317/230 [72] Inventors: Masao Matsuo, Takarazuka; Hiroshi p Emmine,|ameS Kanam Tomiw" Osaka both of Japan Attorney-Eugene E. Geoffrey, Jr.

[73] Assignee: Matsuo Electric Company, Limited, 1

Osaka-fir, Japan [57] ABSTRACT [22] Filed: Jan. 13, 1971 The method ofmaking a capacitor by forming a piece of sheet metal to provide acommonsupport and alternate anode and [211' P 106A" cathode members extendingfrom the support, electrically 7 connecting capacitor elements betweeneach of said anode [52] U.S. Cl ..317/230, 29/570 n cathode m m r ing thindivi al el m n and at [51] Int. Cl. ..H01g 9/05 l ast part of theanode and cathode members with a plastic [58] Field of Search ..317/230,231, 233; 29/570, resin and then severing the members from the commonsup- 29/25.4l port and the resulting capacitor which has the terminalsextending therefrom in substantially parallel relationship.

[56} References Cited 1 i r A 6 Claims, 10 Drawing Figures UNITED STATESPATENTS 3,349,294 10/1967 l-leinimann et a1.. 1 7/230 g z s q s 2 \3 z Iu 4' I I fi Q a i PATENTEI] FEB 2 9 I972 SHEET 2 UF 2 JIR llh

Fig. 7

Fig. 9

SOLID-STATE ELECTROLYTIC CAPACITOR AND MET-HOD OF MAKING SAME tor iscomposed of a capacitor element, a pair of lead conductors bondedthereto and a synthetic resin package enclosing the capacitor elementand a part of the lead conductors. The capacitor element is generallyformed by electrolytically oxidizing the surface of an'anode electrode,which is made of a wire. ora plate of film-forming metal such astantalum, niobium or aluminum or a sintered body of powder of suchmetal, to form a dielectric oxide layer thereon, and then formingfurther a semiconductor layer of manganese dioxide and a cathode layerofcarbon and/or silver in turn thereon. The capacitor element is providedwith a leadout wire made of the same metal as the anode electrode andwelded to or embedded in the anode electrode before it iselectrolytically oxidized. ltisa general practice that the anodeconductor is welded to this-leadout wire and the cathode conductor issoldered to the cathode layer of the element.

In the case of bonding the conductors to the element in mass production,the conductors are generallyarranged in a suitable welding jig. However,since such conductors are generally consisting of thin wires such as of0.3 to 0.6 millimeterdiameter, they are often bent accidentally duringhandling. This has been a great barrier to automation of the processessuch as welding, soldering and resin packaging, as well as tomaintenance and-improvement of geometrical accuracy and electricalfidelity of the products.

Therefore, a main object of this invention is to propose a structure.and a method of manufacture of'a resin-coated solid state electrolyticcapacitor, from which the above-mentioned disadvantages. are completelyeliminated, and which are very suitable for mass production of suchcapacitors.

According to this invention, the anode and cathode conductors of thecapacitor element are formed by punching or etching asheet material of ametal, such as nickel, Kovar (trade name) or copper, which is suitablefor welding and soldering. In the first step, a number of pairs of anodeand cathode conductors are formed in a continuous pattern in which therespective conductors are integrally connected to a common weblike stripand extending to a same side of the trip and. theanode and. cathodeconductors of the each pair and also the respective pairs are properlyspaced from each other.

Each of the anode and cathode conductors has a widened portion provided.for reinforcement of the conductor and improvement of resin holding, andthis portion of the anode conductor hasa projection for welding the leadwire of the capacitor element. The widened portions of the-both anodeand cathode conductors are interconnected by an integral bar in order tofurther reinforce the conductors and to keep the spacetherebetweenaccurately. This connecting bar is cut away after packagingprocess.

Then, capacitor elements are bonded to the respective pairs ofconductors by welding the respective leadwires to the correspondingwelding projections of the respective anode conductors and then dippingthe assembly in a solder bath to solder the cathode conductors tothe'cathode layers of the respective elements. Thereafter, the assemblyis dipped in a molten syrthetic resin-bath to form a resin package onthe each element I Other objects and features of this inventionwill bemore clearly understood from the following description with reference tothe accompanying drawings.

In the drawings:

FIG. I is a cross-sectional view of an embodiment of a solidstateelectrolytic capacitor according to this invention;

FIG. 2' is a view in partial section of the capacitor of FIG. 1

attached to a printed circuit board;

FIGS. 3 through 6 are partly broken away views representing successivesteps of manufacturing the resin-coated solidstate electrolyticcapacitor of FIG. 1;

FIG. 7 is a cross-sectional view of another embodimentof a resin-coatedsolid-state electrolytic capacitor according to this invention;

FIG. 8 is a partly broken-away view representing schematically stepsofmanufacturing the capacitor of FIG. 7;

FIG. 9 is a cross-sectional view of a further embodiment of resin-coatedsolid-state electrolytic capacitor according to the invention; and iFIG. 10 is a partly broken-away view representing schematically steps ofmanufacturing the capacitor of FIG. 9.

Throughout the drawings, same reference numerals are given to likestructural components.

Referring to FIG. .1 representing a typical embodiment of theresin-coated solid state electrolytic capacitor according to thisinvention, there shown is a cylindrical capacitor element 1, having adiameter of about 3 millimeters and a height of about 5 millimeters, forexample. The capacitor element 1 can be prepared by a well-known methodfrom a sintered body of powdered film-forming metal, such as tantalum,niobium or aluminum which serves as the'anode electrode of thecapacitor. A leadout rod 2 of the same metal having a diameter of 0.3 to0.6 millimeters, for example, is previously embedded in or welded tothis body. The body is electrolytically oxidized to form an oxide layeron the whole surface thereof. Then a semiconductor layer of manganesedioxide and a cathode layer of carbon and/or'silver are successivelyformed on the surface of the oxide layer. This is a well-known procedurefor preparing the capacitor element 1 in the prior art and is not thepart of this invention.

The capacitor element 1 is bonded to lead conductors 3 and 4 whichinclude the subject matter of this invention. As will be describedlater, the both conductors 3 and 4 are made by simultaneous punching oretching of a strip of solderable metal, such as nickel, copper or Kovar(trade name), having a thickness of about 0.5 millimeters, for example.The width of the conductors 3 and 4is about 0.5 millimeters, forexample, but the lower portions 5 and 6 thereof are rather widened andhave a width of about 1 millimeter. The widened portions 5 and 6 of theconductors 3 and 4 serve a function of reinforcing the conductors andholding molten resin. The widened portion 5 of the anode conductor 3 hasa, projection 7 extending toward the cathode conductor 4 and welded tothe leadout rod 2 of the element 1', and a downward projection 8 forpreventing the molten resin from being depressed. at this portion. Thewidened portion 6 of the cathode conductor 4 has a projection 9extending downwards and soldered to the surface, i.e., the cathodelayer, of the element I with suitable solder 10. The assembly isenclosed by a synthetic resin coating 11, such as of epoxy resin,leaving a part of the widened portion of the each conductor.

Though, in the drawing, the widened portions 5 and 6 extend in the bothsides of the conductors 3 and 4 respectively, they may extend inone-side thereof as occasion demands,- and the shoulders of the widenedportions may be either squared or rounded. Such variations are all inthe range of this invention.

FIG. 2 shows the above capacitor which is attached to a printed circuitboard 12.The conductors of the capacitor are soldered with suitablesolder 14 to printed conductors 13 of theboard 12. As shown in thedrawing, the shoulders of the widened portions 5 and 6 serveas stoppersfor keeping the height of the attached capacitor constant.

Now, the mass production procedure of such capacitors will be describedin detail with reference to FIGS. 3 through 6.

At first, a thin solderable metal sheet, such as nickel, copper or Kovar(trade name), having a thickness of about 0.5 millimeters, for example,is punched or etched into'a pattern as shown in FIG. 3. In the pattern,a long continuous trunk strip 15 isv provided and a plurality ofbranches extend at a constant interval from one side of the trunk strip15. Each of the branches includes a pair of conductors 3 and 4 extendingsubstantially perpendicularly to the trunk strip 15. The conductors 3and 4 correspond to those in FIG. 1 and have widened portions 5 and 6also corresponding to those in FIG. 1. The widened portions 5 and 6 alsohave various projections corresponding to those 7, 8, and 9 in FIG. 1.

The upper ends of the widened portions 5 and 6 of the both conductors 3and 4 are bridged by a bridge strip 17 which is integral with theseportions 5 and 6. The function of the bridge strip 17 is to reinforcethe narrow conductors 3 and 4 so as not I to be bent or deformed duringthe succee;ing steps of production. The trunk strip 15 has index holes16 bored in correspondence with the respective branches for positioningor indexing the material as occasion demands. 7

'Then, the conductors 3 and 4 are preferably plated with gold, silver,tin or solder for facilitating soldering and other bonding treatments.

Next, as shown in FIG. 4, the capacitor element 1 having the .leadoutrod 2, which is previously prepared as aforementioned, is attached tothe each anode conductor 3 by welding the leadout rod 2 to'theprojection 7. A suitable jig may be used'for positioning the element 1with respect to the conductors 3 and 4 so that the element 1 isappropriately spaced from the projection 8 and in contact with theprojection 9.

' Then, the cathode layer-of the element 1 is soldered to the projection9 of the cathode conductor 4 by dipping about a half of the elementtogether with the projection 9 in molten solder bath. In the resultantassembly, the most surface of the element 1 is coated with solder 10 asshown in FIG. 5.

Next, similar to the soldering step, the assembly is dipped in liquidelectrically insulating synthetic resin, such as epoxy resin, to themiddle of the widened portions 5 and 6 of the conductors 3 and 4 so thatthe bridge strip 17 is left above the liquid surface. Pulling up theassembly from the resin bath and then curing and hardening the resinaccording to a proper well-known schedule, an oval resin package 11 isobtained as shown in FIG. 6.

Since the widened portions 5 and 6 and the various flat projections ofthe conductors 3 and 4 well attract and hold the liquid resin, onedipping is enough to obtain a well-shaped resin package 11 if theconcentration and viscosity of the liquid resin is appropriatelycontrolled. 0n the contrary, according to the prior art, thin wirelikeconductors could not hold a sufficient amount of resin in one dippingand therefore several times of dipping have been required in general forobtaining a well-shaped resin package.

After applying a mark and other indications, the conductors 3 and 4 andthe bridge strip 17 are cut off at the broken lines shown in FIG. 6 anda complete capacitor as shown in FIG. 1 is obtained.

The above-mentioned steps can be carried out according to a batch systemas well as a continuous system.ln the batch system, there is provided alimited length of the trunk strip having a limited number of branchessuch as 10 or 20, and each of the above-mentioned steps is appliedsimultaneously to all of these branches belonging to this trunk strip15. In the continuous system, however, the trunk strip .15 is generallyvery long and has a unlimited length and the number of branches is alsounlimited. Stations for applying the abovernentioned steps respectivelyto the material are arranged on a line and the branches passsuccessively the respective stations continuously and are applied withthe corresponding treatments successively. These systems of productioncan be selected suitable as occasion demands and are not the subjectmatter of this invention.

FIGS. 7 and 9 show variations of the capacitor of FIG. 1 whichrespectively require wide and narrow gaps between the both conductors 3and 4 for convenient use. These capacitors may be produced by use of thepatterns as shown in FIGS. 8 and 10, respectively. In FIG. 8, aconnection strip 18 is provided between the adjoining branches forfurther reinforcing the narrow conductors in addition to the bridgestrip 17.

As easily understo according to th1smventron,improved ing an anode offilm-forming metal and successive coatings of an oxide dielectric layer,a semiconductor layer and a cathode layer thereon, with a leadout rodconnected to said anode, and a pair of lead conductors, connected tosaid rod and cathode layer respectively, extending in a same direction,said method comprising: preparing a plurality of pairs of metal branchesintegral with and extending from one side of a metal strip with each ofsaid branches having a relatively narrow portion near and a relativelywide portion remote from the strip, welding an end portion of saidleadout rod of said capacitor element to the relatively wide portion ofone of the branches in a pair of said conductors, soldering the wideportion of the other branch in said one of the pairs to said cathodelayer, and applying a resin layer over said capacitor element, forforming a package around the element with said metal branchesextendingtherethrough, and separating said metal branches from the metal stripwhereby a pair of branches form lead conductors for the capacitor, withthe relatively wide portions bonded thereto and the relatively narrowportions forming lead terminals therefor;

2. The method according to claim 1 including the steps of forming abridge between each pair of said metal branches and removing saidbridges upon securing said capacitor elements to said pairs of metalbranches.

3. The method according to claim 1 including providing the wide portionsof said other branches with longitudinal extensions and soldering saidextensions to said cathode layers of said capacitor elements.

4. The method according to claim l-including the step of forming indexholes in said metal strip.

5. The method according to claim 1 including the steps of forming abridge between the branches of each pair of branches and removing ,saidbridges upon securing said capacitor elements to said pairs of metalbranches.

6. A resin coated solid-state electrolytic capacitor comprising an anodeof film-forming metal and an electrolytic dielectric oxide film thereon,a layer of semiconductive electrolyte on said film, and a conductivecathode layer on the electrolyte layer, a leadout rod connected to saidanode, a resin package enclosing said anode including said layers, apair of spaced terminal lead conductors extending in the same direction,each of said conductors having a relatively narrow striplike portion anda relatively wide striplike portion with a greater length of therelatively wide portion embedded in the resin of the package, said wideportion of one of said conductors having a lateral portion with saidleadout rod welded thereto said wide portion of the other of said leadconductors having a longitudinal projection soldered to said cathodelayer whereby said terminal lead conductors are bonded to saidcapacitor.

1. A method of manufacturing a resin-coated solid state electrolyticcapacitor including a capacitor element comprising an anode offilm-forming metal and successive coatings of an oxide dielectric layer,a semiconductor layer and a cathode layer thereon, with a leadout rodconnected to said anode, and a pair of lead conductors, connected tosaid rod and cathode layer respectively, extending in a same direction,said method comprising: preparing a plurality of pairs of metal branchesintegral with and extending from one side of a metal strip with each ofsaid branches having a relatively narrow portion near and a relativelywide portion remote from the strip, welding an end portion of saidleadout rod of said capacitor element to the relatively wide portion ofone of the branches in a pair of said conductors, soldering the wideportion of the other branch in said one of the pairs to said cathodelayer, and applying a resin layer over said capacitor element, forforming a package around the element with said metal branches extendingtherethrough, and separating said metal branches from the metal stripwhereby a pair of branches form lead conductors for the capacitor, withthe relatively wide portions bonded thereto and the relatively narrowportions forming lead terminals therefor.
 2. The method according toclaim 1 including the steps of forming a bridge between each pair ofsaid metal branches and removing said bridges upon securing saidcapacitor elements to said pairs of metal branches.
 3. The methodaccording to claim 1 including providing the wide portions of said otherbranches with longitudinal extensions and soldering said extensions tosaid cathode layers of said capacitor elements.
 4. The method accordingto claim 1 including the step of forming index holes in said metalstrip.
 5. The method according to claim 1 including the steps of forminga bridge between the branches of each pair of branches and removing saidbridges upon securing said capacitor elements to said pairs of metalbranches.
 6. A resin-coated solid-state electrolytic capacitorcomprising an anode of film-forming metal and an electrolytic dielectricoxide film thereon, a layer of semiconductive electrolyte on said film,and a conductive cathode layer on the electrolyte layer, a leadout rodconnected to said anode, a resin package enclosing said anode includingsaid layers, a pair of spaced terminal lead conductors extending in thesame direction, each of said conductors having a relatively narrowstriplike portion and a relatively wide striplike portion with a greaterlength of the relatively wide portion embedded in the resin of thepackage, said wide portion of one of said conductors having a lateralportion with said leadout rod welded thereto said wide portion of theother of said lead conductors having a longitudinal projection solderedto said cathode layer whereby said terminal lead conductors are bondedto said capacitor.